What is the appropriate first‑line test for functional ischemia assessment in a patient undergoing longitudinal coronary artery disease (CAD) care?

Functional Ischemia Assessment in Longitudinal CAD Care

For patients with established CAD undergoing longitudinal care, non-invasive functional imaging for myocardial ischemia (stress echocardiography, stress SPECT/PET, or stress CMR) is the appropriate first-line test when reassessment is needed, with the specific modality chosen based on local expertise and patient characteristics. 1

Algorithmic Approach to Test Selection

The 2024 ESC guidelines provide clear direction for functional assessment in chronic coronary syndrome patients 1:

When Functional Testing is Indicated

• If CCTA shows CAD of uncertain functional significance or is non-diagnostic
• When symptoms change or worsen despite medical therapy
• For risk stratification to identify high-risk patients who may benefit from revascularization

Choice of Functional Imaging Modality

All functional imaging modalities are essentially interchangeable in terms of diagnostic accuracy 2, 3. Select based on:

1. Local expertise and availability - this is the primary driver 1
2. Patient-specific factors:
   • Exercise capacity: Use exercise-based testing when possible (most physiological and safest) 2
   • Inability to exercise: Use pharmacological stress (dobutamine or vasodilator) 2
   • Beta-blocker therapy: Does not affect prognostic value of coronary flow velocity reserve (CFVR) but may reduce sensitivity of wall motion abnormalities 2

High-Risk Thresholds Requiring Action

The guidelines specify exact cutoffs for high-risk findings that warrant invasive angiography 1:

• Stress SPECT/PET: ≥10% of LV myocardium showing ischemia
• Stress echocardiography: ≥3 of 16 segments with stress-induced hypokinesia/akinesia
• Stress CMR: ≥2 of 16 segments with perfusion defects OR ≥3 dobutamine-induced dysfunctional segments
• Exercise ECG: Duke Treadmill Score < -10

Critical Caveats

Do not proceed directly to invasive angiography unless the patient has:

• Very high (>85%) clinical likelihood with severe refractory symptoms
• Angina at low exercise levels
• High event risk features 1

Routine wire-based pressure assessment of all vessels during angiography is NOT recommended - only use FFR/iFR (≤0.80/≤0.89) or QFR (≤0.80) selectively for intermediate stenoses 1

Practical Implementation

For longitudinal CAD care, the workflow is:

1. Clinical reassessment determines if testing is needed (symptom change, risk stratification)
2. Functional imaging is first-line (not CCTA, which is for initial diagnosis in lower pretest probability patients)
3. Positive functional test with high-risk features → invasive angiography with selective FFR/iFR
4. Negative or low-risk functional test → optimize medical therapy

The key distinction from initial diagnosis: in established CAD patients, you're assessing functional significance and risk, not ruling out anatomic disease. This makes functional imaging the logical first choice rather than anatomic imaging 1.